The present invention relates generally to hydraulic systems, and more specifically, to a method and apparatus for hydraulic control in an automobile braking system.
For hydraulic systems, forces and velocities are transmitted and controlled by transmitting and controlling fluid pressure and flow in a closed system. Pressure in hydraulic systems is calculated through the equation p=F/A, where p is pressure (psi), F is force (pounds), and A is area (square inches).
Hydraulic systems are currently used in a variety of control systems, such as automobile braking systems.
In typical braking systems, a hydraulic pressure generator (main cylinder) generates a braking pressure through hydraulic fluid lines in response to depression of a brake pedal, thereby operating a braking device mounted on each tire.
For hydraulic control systems, such as rollover stability control (RSC) using the aforementioned braking systems, fast rates of pressure buildup are desirable. For RSC systems, an RSC designated control wheel must have a high pressure build gradient.
To control pressure, the brake unit also includes tire sensors and electronic switching circuits for detection and monitoring of the rotational behavior of the tires and for the generation of electric brake pressure control signals for use in slip and rollover control.
Many hydraulic systems, such as the aforementioned, utilize valves having a switchable orifice size, primarily to improve noise and vibration harshness (NVH). Orifice size or state is typically determined by the pressure difference across one of the valves, switching from a large state to a small state in response to a high pressure difference. Pressure activated valve switching has previously not been directly controllable.
It would therefore be desirable to provide a system and method for preventing an orifice from switching from a large state to a small state during large build requests. It would also be desirable to provide a maximum pressure gradient and to provide direct pressure activated valve switching. The present invention is directed to these ends.